DSG and creeping

[CatonaPC©]

Excellent! Citki, I'm with you on your reasoning that the DSG should not be regarded like a traditional 'slush box' and should be driven accordingly.

For the record I get a bunny hop when it shifts from 3rd to 2nd in D or S. In tiptronic mode, it doesn't happen. I have had it reset once, but it only lasted about 2000kms before it resurfaced. I will try and get it reset again, and see if it cures it, but at this stage, it's only a minor annoyance.

Waiting on logger to get back on his tests.

[blutopless2]

Excellent! Citki, I'm with you on your reasoning that the DSG should not be regarded like a traditional 'slush box' and should be driven accordingly.

sorry if i gave that impression but not once did i state it. i know it has no torque converter so will not behave like a "standard auto".

maybe there is something wrong with mine and i will definitely get it looked at.
just a frustrating gearbox in certain situations.

[logger]

A DSG7 data log

See what you make of this. DSG7 Drive log.xls
Its a speadsheet showing what goes on in a short 4 minute drive in "D" with the TSI118 DSG7 reversing, stopping and starting several times and going through all 7 forward gears. Unfortunately the sample rate is only 1/sec so it is fair to say it misses a lot. Logs the 3 input speeds, 2 clutch positions, Gear in use on each drive shaft, Position of each of the four gear selector forks and vehicle speed.
It is fairly arcane, nothing earth shattering, but I still found it pretty interesting. I think it pretty much shows what I was describing earlier, about neither clutches being fully engaged and both slipping all the way through 1st and well into 2nd gear on doing a gentle start off. Also shows that another gear will not necessarily be pre-selected when driving which I was under the misconception to be the case.
Next log I will do is just a simple one to see "...if the perception of a down change from 2nd to 1st when MFD shows D1 already in use.." is actually just the slip coming out of the k1 clutch attached to 1st gear. I can also say that if the MFD tells you, you are in a gear the vagcom data backs it up as far as I can tell.

I have just about had a brain melt down the past couple of weeks nutting out what means what in VagCom to get this info out. Poring over the 0AM gearbox study guide, staring at spreadsheets of raw numbers in every gear and jacking my car up and spinning the wheels by hand with it in gear, while looking at my laptop. The DSG7 is very different to the DSG6 mechatronic output and there is no decode (label file) available yet to make sense of any of it. So I made my own rudimentary label file by trial and error and I can now tell to some degree what is going on inside. I can actually see a lot more than what is recorded in the SS, it is just that vagcom only lets you log 12 items at a time.

Anyway I hope you guys find it interesting.

[Wolfman_36]

Anyway I hope you guys find it interesting.

Logger - excellent piece of work. It's great to see some hard numbers. BTW - I assume the "STAMP" columns in the raw data are time stamps for the individual data. Therefore, do you think it would be reasonable to standardise the times across the data by linear interpolation to line the numbers up a bit more? Maybe 1 second is too big an interval for this to work..... Just curious.

[cktsi]

See what you make of this. DSG7 Drive log.xls

That's fantastic data... also you went to some lengths to make observations on the topic!

This spreadsheet triggered me to go off & read a couple of technical pages on the DSG that I previously couldn't be bothered reading... all in the quest to understand the low speed bumping

Now that my eyes are sore got a few questions.

I think what I've read about the 6DSG still translates to the 7DSG. Why are there two values for each input shaft? From what I can tell from my readings, the gear wheels on the input shaft are sometimes used for two or more gears... so for example is N5 and N7 referring to the fact that 5th & 7th ,whilst both on input shaft 1 (as it's listed in that column) also happen to share the same gear wheel on shaft 1?

So I think it's saying the pairings are
Input Shaft 1: 1st & 3rd; 5th & 7th.
Input Shaft 2: 2nd & 4th; 6th & Reverse

What does the mysterious xN or Nx indicate?

The one thing this reveals is that the clutch engagement isn't on/off like I thought, but gradual as indicated by the clutch position in mm. That data alone is really informative.

Unfortunately the sample rate isn't high enough to see precisely what's going, but what could be creating the 'bumping' sensation at really slow steep incline crawls if the DSG is in fact able to finely modulate the travel of the clutch (contrary to what I believed)?

I've done a lot of searching this morning, but couldn't find anything to explain this... used terms such as DSG crawl, DSG prevent stall, DSG creep etc

btw you've debunked what the VW tech said about not being able to log normal operational running & only being able to capture faults. You can with vagcom

[logger]

Should have mentioned there are two sheets in the XLS. It may open to the less easy to understand "raw data" sheet. The "DSG7 Drive log" sheet is the easier one to understand. Anyway you blokes seem to have worked it out.

Logger - excellent piece of work. It's great to see some hard numbers. BTW - I assume the "STAMP" columns in the raw data are time stamps for the individual data. Therefore, do you think it would be reasonable to standardise the times across the data by linear interpolation to line the numbers up a bit more? Maybe 1 second is too big an interval for this to work..... Just curious.

Thanks mate. Yes that is correct. I think this interpolation would work OK for RPMs and things that change relatively slowly. But not for positions and selections which can change in a nanosecond. The interpolation could still show the wrong position. I can get my sample rate up to 10per sec which is nearly good enough, but have to sacrifice fields to do so. If I only look at 2 gears instead of all 8 in will improve.

That's fantastic data... also you went to some lengths to make observations on the topic!

This spreadsheet triggered me to go off & read a couple of technical pages on the DSG that I previously couldn't be bothered reading... all in the quest to understand the low speed bumping

Now that my eyes are sore got a few questions.

I think what I've read about the 6DSG still translates to the 7DSG. Why are there two values for each input shaft?

Do you mean N+N being 2 values on gear selected or something else? If so Left hand number 1/2/3/4N, indicates the gears that live on Output shaft 1 and NR/5/6/7, gears that live on Output shaft 2.

From what I can tell from my readings, the gear wheels on the input shaft are sometimes used for two or more gears... so for example is N5 and N7 referring to the fact that 5th & 7th ,whilst both on input shaft 1 (as it's listed in that column) also happen to share the same gear wheel on shaft 1?

No - as above - just means the two gears live on the same output shaft. Only shared gear wheel in the DSG7 are 6&4 and 2&R in input shaft 2 (D2). So D2 has two gears wheels whereas D1 has four, one for each gear 1,3,5,7.

So I think it's saying the pairings are
Input Shaft 1: 1st & 3rd; 5th & 7th.
Input Shaft 2: 2nd & 4th; 6th & Reverse

Yep thats right. But it easy to melt your brain down getting your head around it all. Odd gears on one input shaft (and clutch) even on other, while at the same time low 4 gears on one output shaft with high 3 gears plus R on other.

What does the mysterious xN or Nx indicate?

Gear in change in progress I expect

The one thing this reveals is that the clutch engagement isn't on/off like I thought, but gradual as indicated by the clutch position in mm. That data alone is really informative.

Unfortunately the sample rate isn't high enough to see precisely what's going, but what could be creating the 'bumping' sensation at really slow steep incline crawls if the DSG is in fact able to finely modulate the travel of the clutch (contrary to what I believed)?

I should be able to get you some good data on this @ 0.1sec intervals by simply zeroing in and looking at a single clutch

I've done a lot of searching this morning, but couldn't find anything to explain this... used terms such as DSG crawl, DSG prevent stall, DSG creep etc

btw you've debunked what the VW tech said about not being able to log normal operational running & only being able to capture faults. You can with vagcom

Yeah that is BS hey! I think it may be the case for the VW VAG tool but for VAGCom whish Ross tech use as a selling point.
Glad you blokes liked it BTW. Means it is worth while to make some more. Prolly should put future stuff I do in MK6 thread though, or does MK5 twincharger have the DSG7 too?

[blutopless2]

The one thing this reveals is that the clutch engagement isn't on/off like I thought, but gradual as indicated by the clutch position in mm. That data alone is really informative.

so this information makes what my dsg does even more puzzling.

looks like its definitely going back to the dealer for a checkup.

[cktsi]

No - as above - just means the two gears live on the same output shaft. Only shared gear wheel in the DSG7 are 6&4 and 2&R in input shaft 2 (D2). So D2 has two gears wheels whereas D1 has four, one for each gear 1,3,5,7.

Oh, so when you were talking about D1 and D2, sometimes you were referring the drive shaft (i.e. input shaft)? I re-read your previous posts and think I got it when you were referring to D1 on the MFD as opposed to the drive shaft 1.

When you say

Perhaps the lurch felt when whacking the selector from D1 to 1st (Tiptronic) in this transition phase is the respective clutch aborting the impending gear change and removing all slip on K1.

I've actually noticed that my car crawls in "D2" on MFD and when I gear down to 1st via tiptronic I get the lurch.

Either way, both scenarios of D1 to 1st and D2 to 1st would be interesting to log.

I've also noticed that when creeping in my car, the DSG will only momentarily be in D1 and when there's enough road speed it will crawl in D2... even climbing steep inclines!! Of course if I get to stalling speed it kicks down to D1 and does the bumping.... but it would be interesting to see what the clutch travel shows on your vagcom when crawling in D2 (and whether there's slip or not).

Yeah... probably worthwhile starting a Mk6 thread since a lot of your observations are more for 7DSG (tho still relevant for any other DSG)

But it easy to melt your brain down getting your head around it all. Odd gears on one input shaft (and clutch) even on other, while at the same time low 4 gears on one output shaft with high 3 gears plus R on other.

It's taken a morning of flipping back & forth between the pages describing the function of the 2 shafts & the final diagram showing the flow of torque in each gear via the whole DSG, but I think I've finally got it sorted.

Yeah... whether it's the 02E or 0AM, looks like they group the high gears together on the output shaft... presumably the diameter is physically smaller for those higher gears.

Also, I never realised the twin clutches were concentric... I thought there were physically two adjacent clutches !! It's a very clever set up having the two input shafts one inside the other.

[logger]

Oh, so when you were talking about D1 and D2, sometimes you were referring the drive shaft (i.e. input shaft)? I re-read your previous posts and think I got it when you were referring to D1 on the MFD as opposed to the drive shaft 1.

Yes Sorry, I was indeed using D1/D2 to describe input drive shafts as well as the indicated gear. I had being had been using D1,D2,K1,K2,O1,O2 in my shorthand when working which bit was which.

I've actually noticed that my car crawls in "D2" on MFD and when I gear down to 1st via tiptronic I get the lurch.

I can sort of understand you getting the lurch when you do that, as you are forcing it down to 1st without it having a chance to match the revs.

Either way, both scenarios of D1 to 1st and D2 to 1st would be interesting to log.

Can you spell out these 2 scenarios. What do you mean by "D1 to 1st"? If D1 is displayed it should already be in 1st shouldn't it? Just so I know what you are after.

I've also noticed that when creeping in my car, the DSG will only momentarily be in D1 and when there's enough road speed it will crawl in D2... even climbing steep inclines!! Of course if I get to stalling speed it kicks down to D1 and does the bumping.... but it would be interesting to see what the clutch travel shows on your vagcom when crawling in D2 (and whether there's slip or not).

Will take a look for you.

[gerhard]

Gawd, just come back from a couple of days away and there's so much excellent info here my brain started bleeding

Will definitely re-read all and digest when I'm a bit fresher.

Backtracking a bit to the comments about clutches lasting for "life" - that's not as far-fetched as some seem to think. A traditional auto transmission has lots of multi-plate clutches in it, and they last for "life", and they are many times smaller than the DSG's twin clutches.

[logger]

... it would be interesting to see what the clutch travel shows on your vagcom when crawling in D2 (and whether there's slip or not)

Yes there is slip alright.
Did some quick testing. Flat road, Foot off Accelerator throughout. Let car accelerate to stabilise @ 6kph then stop. 3 separate Times:
1) in Drive with "D1" then "D2" displayed to 6kph then stop.
2) in Tiptronic with "1" displayed to 6kph then stop.
3) in Drive with "D1" then "D2" displayed to 6kph then flip to Tiptronic, whence "1" displays automatically, then stop.

In Tiptronic "1" driveshaft 1 got within 150 rpm of the Eng RPM indicating some slip, but in "D2", driveshaft 2 never even gets as high as 50% of ENG rpm indicating a lot of slip! Was not as though the car feels like it will acellerate past 6kph in this state either. It will just keep on slipping the clutch I guess.

Will post the logs tomorrow.

[cktsi]

Can you spell out these 2 scenarios. What do you mean by "D1 to 1st"? If D1 is displayed it should already be in 1st shouldn't it?

Actually, I thought in an earlier post you were talking about D1 to 1st?

While it is still indicating D1 if I flip it to tiptronic a very obvious downshift from 2 to 1 occurs. .

Anyway... doesn't really matter because your last paragraph sums it up nicely and gels with what we've observed with 7DSG 0AM

In Tiptronic "1" driveshaft 1 got within 150 rpm of the Eng RPM indicating some slip, but in "D2", driveshaft 2 never even gets as high as 50% of ENG rpm indicating a lot of slip! Was not as though the car feels like it will acellerate past 6kph in this state either. It will just keep on slipping the clutch I guess.

Have to say that your research has been tireless & exhaustive. I reckon this is the only place in the internet where you definitively have sufficient facts to back up the observations to describe what's really going on in the DSG when it creeps / crawls. Well done!!

I guess we'll see more answers in the Mark 6 forum. I'm rarely in heavy bumper to bumper traffic as I don't drive in peak hour, but today got caught up in it. In D1 it was doing some slight bumping (tho not to the same extent as what blutopless2 may be having).

btw blutopless2... have you had it checked out? I hope the bumping only shows up in rare situations like steep inclines. Hopefully it's not as pronounced on slight inclines or level road.

[logger]

...Have to say that your research has been tireless & exhaustive. I reckon this is the only place in the internet where you definitively have sufficient facts to back up the observations to describe what's really going on in the DSG when it creeps / crawls. Well done!!

Thanks... I think its because I am the only silly bloke who has melted his brain making a working VagCom label file for the DSG7 at the moment. I see people have been asking for this file since way back in Jan this year. Ross-Tech will do doubt eventually provide a proper one and it will be a S load better than mine. In the mean time I am it. Continued on the MK6 thead..

[blutopless2]

btw blutopless2... have you had it checked out? I hope the bumping only shows up in rare situations like steep inclines. Hopefully it's not as pronounced on slight inclines or level road.

haven't booked it into dealer yet... lots going on with the birth of our daughter so hope to get it booked in the next few weeks...

the lurching that i experience with it happens at low speed (not sure of the actual kmh) even on a flat surface whilst it is indicating in 2nd gear and the revs are down near idle. the rev counter rises to about 1200 then you feel the car surge forward and the revs drop (as if it is slipping the clutch to move forward ) but then the revs rise back up to 1200 like it has disengaged the clutch and then repeats the slipping so the car surges forward then slows then surges and all this happens quickly so it feels really rough as a passenger like you are bunny hopping. from outside of the car it must look like you are driving a manual for the first time.
i understand that its trying to maintain a low speed etc... but why would it not hold 1st gear or just hold a constant slip on the clutches in 2nd?
this is why i have to get it looked at... has become so frustrating coz aside from low speed control the gearbox is really good.
was hoping my next car to be an R36... but these issues with the gearbox make me want to stay away from a DSG car in future.
will keep you posted on what happens at the dealer.

[cktsi]

haven't booked it into dealer yet... lots going on with the birth of our daughter so hope to get it booked in the next few weeks...

Congrats!

the rev counter rises to about 1200 then you feel the car surge forward and the revs drop (as if it is slipping the clutch to move forward ) but then the revs rise back up to 1200 like it has disengaged the clutch and then repeats the slipping so the car surges forward then slows then surges and all this happens quickly so it feels really rough as a passenger like you are bunny hopping.

What are you doing with the accelerator while this is happening? Is your foot completely off or are you applying throttle?

I'm assuming that either your foot is off or you are feeding a constant amount... and I haven't seen that behaviour in my car.

Which engine & DSG type do you have in your jetta? (sorry, not familiar with Jetta TSI DSG... could mean the 1.4 TSI or 2.0TFSI with 7DSG or 6DSG respectively)